This invention relates to polyester articles having improved barrier properties and heat sealability, and more particularly relates, in a preferred embodiment, to polyester packaging films coated with a saran composition.
Polyester films, and especially polyethylene terephthalate films oriented by stretching and/or drawing in both directions, are versatile materials due to their high strengths and general chemical inertness. These films have been somewhat deficient for use in packaging, however, due to their poor heat sealability and relatively high water vapor permeability.
The term saran applies to a family of vinylidene chloride homopolymers and copolymers with other ethylenically unsaturated monomer(s). Saran is a well known coating material used to impart water vapor impermeability and heat sealability to various substrates, including packaging films. When used as a barrier coating on polyester films, however, the saran has a tendency to delaminate from the film. This delamination has somewhat restricted the usefulness of saran coated polyester films despite their otherwise excellent properties.